Chain stitch device for lock stitch sewing machines



March 16, 1965 E. H. DOERNER CHAIN STITCH DEVICE FOR LOCK STITCH SEWINGMACHINES 3 Sheets-Sheet 1 Filed Aug. 7, 1963 R m E V W.

ERNEST H. DOERNER WITNESS TTORNE Y March 16, 1965 E. H. DOERNER CHAINSTITCH DEVICE FOR LOCK STITCH SEWING MACHINES Filed Aug. '7, 1963 3Sheets-Sheet 2 Fig.4

INVENTOR. ERNEST H. DOERNER I (fa-M ATTORNEY March 16, 1965 E. H.DOERNER CHAIN STITCH DEVICE FOR LOCK STITCH SEWING MACHINES 3Sheets-Sheet 3 Filed Aug. 7, 1963 I N VENTOR. ERNEST H. DOERNER WITNESSATTORNEY United States Patent Ofitice 3,173,391 CHAIN STITCH DEVICE FQRLOCK STITCH SEWING MACHINES Ernest H. Doerner, Morris Plains, N.J.,assignor to The Singer Company, New York, N.Y., a corporation of NewJersey Filed Aug. 7, 1963, Ser. No. 300,561 4 Claims. (Cl. 112-468) Thisinvention relates to sewing machines, and more particularly, to devicesfor converting a lock stitch sewing machine into a chain stitch sewingmachine.

It is an object of this invention to provide devices attachable to alock stitch sewing machine for converting the machine to chain stitchformation.

A further object of this invention is to provide chain stitch conversiondevices comprising stationary elements fixedly secured relatively to thesewing machine frame and adapted to cooperate with the regular lockstitch forming instrumentalities of the sewing machine including needle,loop taker, needle thread take-up and work feeding mechanism unalteredin structure or cooperative relation from that required for theformation of lock stitches.

A still further object of this invention is to provide chain stitchconversion device-s of the above character supported on a throat plateexchangeable on a lock stich sewing machine to elfect the conversion tochain stitch formation.

The accompanying drawings illustrate a preferred embodiment of thisinvention in which:

FIG. 1 represents a head end elevational view of a lockstitch sewingmachine with the bracket arm cover plate removed and portions of the bedbroken away to illustrate the stitch forming instrumentalities havingthe chain stitch conversion device of this invention applied thereto,

FIG. 2 represents an enlarged top plan view of a portion of the worksupporting bed of the sewing machine of FIG. 1 with the throat plateremoved and the bed slide withdrawn to expose the stitch forming instrumentalities within the bed.

FIG. 3 is a detached perspective view of the elements carried on thethroat plate which comprise the chain stitch conversion fittings of thisinvention,

FIG. 4 is a bottom plan view of the throat plate with the chain stitchfittings of this invention applied thereto,

FIG. 5 is an elevational view taken substantially along line 5-5 of thethroat plate assembly of FIG. 4,

FIG. 6 represents a perspective view of fragments of the stitch forminginstrumentalities of the sewing machine of FIG. 1 with the chain stitchconversion device of this invention including the needle thread andillustrating the position of parts and thread at needle penetrationduring the formation of chain stitches,

FIG. 6A represents a vertical cross sectional view taken substantiallyalong line 6A6A of FIG. 6,

FIG. 7 represents a perspective view of fragments of the stitch forminginstrumental-ides of the sewing machine similar to that of FIG. 4 butwith the position of parts and thread illustrated shortly after needleloop seizure during the formation of chain stitches,

FIG. 7A is a vertical cross sectional view taken substantially alongline 7A7A of FIG. 7,

FIG. 8 represents a perspective view of fragments of the stitch forminginstrumentalities of the sewing machine similar to that of FIG. 4 butwith the position of parts and thread illustrated at the upstroke of theneedle and after the seized needle thread loop has been cast off theloop taker beak, and

FIG. 8A is a vertical cross sectional view taken substantially alongline 8A8A of FIG. 8.

Patented Mar. 16, 1965 This invention provides for the conversion tosingle thread chain stitch sewing of a conventional lock stitch sewingmachine. FIG. 1 illustrates a head end elevational view of aconventional household lock stitch sewing machine to which thisinvention may be applied.

The sewing machine frame includes a bed 11 from which rises a standard12 supporting a bracket arm 13 overhanging the bed. A main shaft 14journaled lengthwise in the bracket arm drives all of the moving partsof the sewing machine and may be actuated by an electric motor (notshown), by foot treadle or the like.

A counterbalanced crank 15 on the mainshaft 14 is operatively connectedby means of a drive link 16 to a needle bar 17 endwise slidable in abearing 18 in the bracket arm and carrying at its lower extremity an eyepointed needle 19. The crank 15 also actuates .a needle thread take-uplever 20 of which the motion is constrained by an anchor link 21. Thepath of a needle thread passes from a supply (not shown) to a threadtensioning device 22, through an eyelet 23 in the take up lever 20, andthen through appropriate guides such as the thread guide 24 on theneedle bar 17 and to the needle eye. This needle thread controlarrangement is typical of that which is required for lock stitchformation. The use of the chain stitch conversion devices of thisinvention will operate successfully, however, with such lock stitch typeneedle thread controls.

Journaled in the bed on a loop taker shaft 30 is a loop taker indicatedgenerally at 31. The loop taker illustrated in the drawings is avertical axis rotary hook adapted to partake of two revolutions for eachreciprocation of the needle. The loop taker is formed with a cup shapedbody portion 32 formed with an inwardly extending loop seizing beak 33adapted to engage and manipulate loops of thread from the needle 19which as illustrated in FIG. 2 rcciprocates in a path which passesinwardly of the cup shaped loop taker body portion.

A bobbin case 34 is journaled within the loop taker body portion 32 andconstrained against rotation therewith by means of a rotationrestraining assembly 35 including a spring 36 which engages an abutment37 on the bobbin case 34-. A bobbin accommodating cavity 38 is formed inthe bobbin case within which a conventional thread carrying bobbin(notshown) may be placed with freedom to rotate.

The needle and loop taker thus far described are capable of producinglock stitches in a conventional manner. The loop seizing beak 33 of theloop taker will engage and carry loops of needle thread completely aboutthe bobbin case and thus if a threaded bobbin is in place in the bobbincase the needle and bobbin threads will be concatenated into true lockstitches (Federal type #301) following each needle penetration. The looptaker may be driven at two revolutions for each needle reciprocation bymeans of a shaft 40 in the standard 12 driven by bevel gears 41 from themainshaft and con nected in turn by bevel gears 42 to a bed shaft 43which drives the loop taker shaft 30 by a set of bevel gears 44.

Illustrated in FIG. 1 is a work feeding mechanism of the drop feedvariety. A feed dog 49 formed with a transverse web 50 operates throughslots 51 in a throat plate 52 and is secured by screws 53 to a feed bar54 beneath the bed. Feed advance and return movements are imparted tothe feed bar from an oscillating feed advance rock shaft 55 connected tothe feed bar by means of a rock arm 56. The feed advance rock shaft 55is oscillated by means of conventional connections 57 in the standardfrom a feed cam 58 on the mainshaft 14. The connections 57 may includeconventional regulating means 59 for varying the stitch length. Risingand falling motion is imparted to the feed bar from an oscillating feedlift rock shaft 60 in the bed. The feed lift rock shaft 60 is providedwith a rock arm 61 connected by means of a link 62 to the feed bar 54.The feed lift rock shaft is oscillated by means of conventionalconnections 63 in the standard from a feed lift eccentric 64 on themainshaft 14. It will be appreciated that as is conventional in the artthe work feeding mechanism is timed relatively to the needlereciprocation so that the feed dog is lifted and advanced while theneedle is raised out of any work on the throat plate, and the feed dogis lowered beneath the throat plate and returned while the needledescends.

Referring to FIGS. 2-5, the conversion device for rendering the abovedescribed lock stitch sewing machine suitable for sewing chain stitchesincludes a rigid metal bracket 70 secured beneath the throat plate 52 byscrews 71. The bracket 76* extends transversely across the throat platein front of the feed dog slots 51 in a shallow recess 72 formed beneaththe throat plate. Bent downwardly therefrom so as to depend from thebracket '76 in front of a needle aperture 73 in the throat plate is athread loop engaging finger 74. The side edges 75 of the thread loopengaging finger preferably diverge slightly from the bracket 70downwardly so as to deter inadvertent dropping of a thread looptherefrom as will be explained hereinbelow.

Also secured beneath the throat plate 52 by the screws 71 is a leafspring 76 which extends parallel to the bracket 70 and is boweddownwardly therefrom. At the extremity opposite the securing screws 71,the leaf spring is formed with an inturned portion 77 adapted slidablyto embrace the bracket 70 in a notch 78 formed in the bracket. The leafspring 76 forwardly of the thread loop engaging finger 74 is formed witha downwardly extending protrusion 79 which is preferably arrangedslightly toward the right hand side of the thread loop engaging finger74 as viewed in FIGS. 2 and 5.

Referring to FIGS. 2, 6 and 6A, a leaf spring 8t) is secured by a screw81 to the bobbin case 34 on that side of the bobbin accommodating cavity38 which faces the path of needle reciprocation. The leaf spring 8%)extends generally parallel to the bracket 70 and the leaf spring 76associated with the bracket when the bobbin case is properly restrainedwithin the loop taker. An abutment projection 82 formed on the bobbincase extends over a portion of the leaf spring 80 as illustrated inFIGS. 6 and 6A, thus providing a stop limiting the upward position ofthe free extremity of the leaf spring 80. When the throat plate 52 issecured on the sewing machine bed the protrusion 79 on the leaf spring76 engages the projection 82 and the. thread loop engaging finger 74engages and shifts the leaf spring 80 downwardly away from the stopprojection 82.

Referring to FIGS. 6, 7 and 8 and the companion FIGS. 6A, 7A and 8A, theoperation of a sewing machine fitted with the chain stitch conversiondevice of this invention will now be described.

FIGS. 6 and 6A illustrate the position of the parts of the sewinginstrumentalities during the formation of chain stitches andparticularly during that portion of a stitch forming cycle when theneedle is penetrating the work at S. The feed dog 49 will occupy arearward position toward the left as viewed in FIG. 6A, having justcompleted a feed stroke, and will be starting to drop out of engagementwith the work. The needle 19 will have carried through the work at S andthrough a needle aperture 73 in the throat plate a loop of thread ofwhich a supply limb T leads to the thread guide 24, take up eyelet 23,tension device 22 and thence to the supply, and a work limb T leads tothe previous needle penetration 8-1 in the work. Tracing the work limb Tof the new needle thread loop T T beyond the previous needle penetrationS4 in the work it will form a thread loop T which extends under the feeddog web 59 and around the thread loop engaging finger 74-. The newneedle thread loop T T will be carried by the needle feed dog upon beinglowered and moved toward the thread loop engaging finger 74 during thereturn stroke of the feed dog will have forced the thread lop Tdownwardly on the thread loop engaging finger 74, the loop T being heldonly by the constraining influence of the spring 3% FIGS. 8 and 8Aillustrate the positions as the needle nears the top of its stroke. Thenew needle thread loop T T will have been carried by the loop taker beakcompletely about the bobbin case 34 and in so doing will have appliedsufficient tension to the thread loop T as to draw the loop T betweenthe finger 74 and the leaf spring 86. The take up lever 20 will act todraw the loop T T taut but while any slack remains the new needle threadloop T T will be constrained by the protrusion 79 on the interengagingleaf spring 76 and the abutment 82, as illustrated in FIGS. 8 and 8A,and will not fall between the bobbin case 34 and the thread loopengaging finger 74. The feed dog 49 will be raised into engagement withthe work and partaking of a feed advance stroke.

As the sewing machine take-up lever 20 sets the stitch, the new needlethread loop T T will be drawn taut and pulled between the abutment 82and the protrusion 79 on the leaf spring 76. The thread loop T T willthen snap onto the thread loop engaging finger 74. The thread loop oncetaut on the finger 74- will remain thereon until it is forced downwardlyand off the finger by the thread stripping action of the feed dog web50.

When the needle again penetrates the work, what had been the new needlethread loop T T becomes the detained thread loop T as illustrated inM65. 6 and 6A thus completing a cycle of chain stitch forming operation.

Since the lop taker 31 will carry needle thread loops completely aboutthe bobbin case 34 during chain stitch formation using the conversionfittings of this invention, just as in lock stitch formation, a threadcarrying bobbin if placed in the bobbin case cavity 38 will deliver alocking thread to the chain stitch seam. When chain stitching, however,the bobbin or locking thread will not be drawn tightly into the work asin lock stitching because in chain stitching the stitches are set duringeach succeeding needle penetration. In chain stitching therefore, thebobbin or locking thread will reeve through the chain stitch loops onthe underside of the work and may be severed and drawn out convenientlyto permit the chain stitch seam to ravel if desired.

To convert the lock stitch sewing machine for chain stitching with theconversion fittings of this invention, it is only required that theconventional throat plate used for lock stitch formation be exchangedfor the throat plate as illustrated in FIGS. 4 and 5 having the elements70 and 76 secured thereto. The spring on the bobbin case is compatiblewith both lock and chain stitch formation and thus the same bobbin case34 may be used for either lock or chain stitch formation.

In lock stitch formation, a round needle aperture in the throat plate isconventional. In chain stitch formation, an elongate needle aperture 73as illustrated in the drawings is preferable to provide clearance forthread movement in the delayed setting of the stitches.

Having thus set forth the nature of this invention what is claimedherein is:

1. In a sewing machine having lock stitch forming instrumentalitiesincluding a frame having a work support formed with a needle aperture, athread-carrying eyepointed needle supported above the work support forendwise reciprocation through said needle aperture, a circularly movingloop taker disposed below said work support, means for driving saidneedle and loop taker in timed relation for the seizure of a loop ofthread from the eye of the needle by said loop taker during each strokeof the eedle downwardly through said needle aperture and the release ofsaid seized loop by the loop taker during each succeeding upward strokeof the needle, a bobbin supporting case journaled in said loop taker,stop means sustained on said frame for constraining said bobbinsupporting case from circular movement with said loop taker, and alinear Work feeding mechanism effective to advance work fabric on saidwork support in one direction from said needle aperture between eachneedle penetration thereof, means for sewing chain stitches using threadcarried by said needle comprising a stationary thread loop engagingfinger carried by said frame and having a free extremity extending in adirection from said work support substantially parallel to said path ofendwise needle reciprocation and arranged at that side of said path ofneedle reciprocation which is opposite the direction of advancement ofwork fabric by said work feeding mechanism, needle thread take-upmechanism effective alternately to draw tight and slacken said needlethread, opposed spring means and spring abutment means arranged betweensaid frame and said bobbin case on that side of said thread loopengaging finger which is opposite to said needle aperture forresiliently constraining passage of thread loops from said loop takeronto said thread loop engaging finger until said thread loops are drawntaut by said needle thread take-up mechanism, a stripping elementdisposed between said thread loop engaging finger and the path ofendwise reciprocation of said needle, and means for reciprocating saidstripping element in timed relation with said endwise reciprocation ofsaid needle and toward the free end of said thread loop engaging fingeras said needle penetrates said needle aperture.

2. In a device as set forth in claim 1, in which said spring abutmentmeans is carried by said bobbin case and said spring means comprises aleaf spring secured relatively to said sewing machine frame bearingresiliently against said abutment means.

3. A device as set forth in claim 1 in which the sewing machine frame isfitted with a removable throat plate formed with said needle apertureand in which said stationary thread loop engaging finger is fixedbeneath said throat plate.

4. In a sewing machine having lock stitch forming instrumentalitiesincluding a frame having a work support formed with a needle aperture, athread-carrying eyepointed needle supported above the work support forendwise reciprocation through said needle aperture, a circularly movingloop taker carried below said work support on an axis substantiallyparallel to the path of end- Wise reciprocation of said needle, meansfor driving said needle and loop taker in timed relation for the seizureof a loop of thread from the eye of the needle by said loop taker duringeach stroke of the needle downwardly through said needle aperture andthe release of said seized loop by the loop taker during each succeedingupward stroke of the needle, a bobbin supporting case journaled in saidloop taker, stop means sustained on said frame for constraining saidbobbin supporting case from circular movement with said loop taker, anda linear work feeding mechanism effective to advance work fabric on saidwork support in one direction from said needle aperture between eachneedle penetration, means for sewing chain stitches using thread carriedby said needle comprising a stationary thread loop engaging fingercarried by said frame and having a free extremity extending in adirection from said work support substantially parallel to said path ofendwise needle reciprocation and arranged at that side of said path ofneedle reciprocation which is opposite the direction of advancement ofwork fabric by said work feeding mechanism, needle thread take-upmechanism effective alternately to draw tight and slacken said needlethread, a projection on said bobbin case, a first leaf spring securedrelatively to said frame adjacent to said thread loop engaging finger,said first leaf spring being bowed into resilient engagement with saidbobbin case projection on that side of said thread loop engaging fingerwhich is opposite to said needle aperture for constraining passage ofthread loops from said loop takeronto said thread loop engaging fingeruntil said thread loops are drawn taut by said needle thread take-upmechanism, a second leaf spring secured on said bobbin case andextending therefrom into abutting relation beneath said thread loopengaging finger, a thread stripping element disposed between said threadloop engaging finger and the path of endwise reciprocation of saidneedle, and means for reciprocating said stripping element in timedrelation with said endwise reciprocation of said needle and toward thefree end of said thread loop engaging finger as said needle penetratessaid needle aperture.

References Cited by the Examiner UNITED STATES PATENTS 1,014,033 1/12Baker 112197 2,999,472 9/61 Yamano 112-168 FOREIGN PATENTS 58,545 1/ 91Germany. 809,217 2/59 Great Britain.

JORDAN FRANKLIN, Primary Examiner.

1. IN A SEWING MACHINE HAVING LOCK STITCH FORMING INSTRUMENTALITIESINCLUDING A FRAME HAVING A WORK SUPPORT FORMED WITH A NEEDLE APERTURE, ATHREAD-CARRYING EYE-RT POINTED NEEDLE SUPPORTED ABOVE THE WORK SUPPORTFOR ENDWISE RECIPROCATION THROUGH SAID NEEDLE APERTURE, A CIRCULARLYMOVING LOOP TAKER DISPOSED BELOW SAID WORK SUPPORT, MEANS FOR DRIVINGSAID NEEDLE AND LOOP TAKER IN TIMED RELATION FOR THE SEIZURE OF A LOOPOF THREAD FROM THE EYE OF THE NEEDLE BY SAID LOOP TAKER DURING EACHSTROKE OF THE NEEDLE DOWNWARDLY THROUGH SAID NEEDLE APERTURE AND THERELEASE OF SAID SEIZED LOOP BY THE LOOP TAKER DURING EACH SUCCEEDINGUPWARD STROKE OF THE NEEDLE, A BOBBIN SUPPORTING CASE JOURNALED IN SAIDLOOP TAKER, STOP MEANS SUSTAINED ON SAID FRAME FOR CONSTRAINING SAIDBOBBIN SUPPORTING CASE FROM CIRCULAR MOVEMENT WITH SAID LOOP TAKER, ANDA LINEAR WORK FEEDING MECHANISM EFFECTIVE TO ADVANCE WORK FABRIC ON SAIDWORK SUPPORT IN ONE DIRECTION FROM SAID NEEDLE APERTURE BETWEEN EACHNEEDLE PENETRATION THEREOF, MEANS FOR SEWING CHAIN STITCHES USING THREADCARRIED BY SAID NEEDLE COMPRISING A STATIONARY THREAD LOOP ENGAGINGFINGER CARRIED BY SAID FRAME AND HAVING A FREE EXTREMITY EXTENDING IN ADIRECTION FROM SAID WORK SUPPORT SUBSTANTIALLY PARALLEL TO SAID PATH OFENDWISE NEEDLE RECIPROCATION AND ARRANGED AT THAT SIDE OF SAID PATH OFNEEDLE RECIPROCATION WHICH IS OPPOSITE THE DIRECTION OF ADVANCEMENT OFWORK FABRIC BY SAID WORK FEEDING MECHANISM, NEEDLE THREAD TAKE-UPMECHAMISM EFFECTIVE ALTERNATELY TO DRAW TIGHT AND SLACKEN SAID NEEDLETHREAD, OPPOSED SPRING MEANS AND SPRING ABUTMENT MEANS ARRANGED BETWEENSAID FRAME AND SAID BOBBIN CASE ON THAT SIDE OF SAID THREAD LOOPENGAGING FINGER WHICH IS OPPOSITE TO SAID NEEDLE APERTURE FORRESILIENTLY CONSTRAINING PASSAGE OF THREAD LOOPS FROM SAID LOOP TAKERONTO SAID THREAD LOOP ENGAGING FINGER UNTIL SAID THREAD LOOPS ARE DRAWNTAUT BY SAID NEEDLE THREAD TAKE-UP MECHANISM, A STRIPPING ELEMENTDISPOSED BETWEEN SAID THREAD LOOP ENGAGING FINGER AND THE PATH OFENDWISE RECIPROCATION OF SAID NEEDLE, AND MEANS FOR RECIPROCATING SAIDSTRIPPING ELEMENT IN TIMED RELATION WITH SAID ENDWISE RECIPROCATION OFSAID NEELDE AND TOWARD THE FREE END OF SAID THREAD LOOP ENGAGING FINGERAS SAID NEEDLE PENETRATES SAID NEEDLE APERTURE.